Nvidia SLI OR ATI Crossfire - Which better for gaming?

I'm in the process of buying PC parts for a new GAMING computer i'm going to build myself. I'm building it for games like WoW and CS:S. I've got the CPU, PSU, And all that stuff. But, I was in a discussion today about Graphics cards. I was originally going for the

"Default" settings, Crossfire beats SLI in a number of titles. If you adjust the shimmer-ful NVidia "Default" settings to remove texture crawl/moire and shimmering, Crossfire then beats SLI in just about everything else.

Also, as already mentioned, ATI cards can do HDR and AA. I don't know why anyone would want to shell out for TWO videocards yet be minimized to not using AA with HDR.

And on the "extra" hardware... Crossfire uses the PCI-Express bus for compositing, which absolutely has more bandwidth than some 16-bit connecting cable hehehe. Overall though, either does the job more than adequately. Not having the cable, of course, does require ATI to have a "Crossfire Master" card though as it's the one that will do the compositing.